Blade drive device and optical instrument

There is provided a blade drive device including a substrate that has an opening, a front curtain and a rear curtain that are movable along an opening surface of the opening so as to open and close the opening, a front curtain locking portion that interlocks with opening and closing operations of the front curtain, a rear curtain locking portion that interlocks with opening and closing operations of the rear curtain, and a regulation lever that is configured to be pivotally movable around a lever axis, and that is capable of entry and escape between an entry position which enters each operation trajectory of the front curtain locking portion and the rear curtain locking portion in response to the opening and closing operations of the front curtain and the rear curtain and an escape position escaped from the operation trajectory. The regulation lever has a front curtain regulation portion which can be locked by the front curtain locking portion from one side around the lever axis at the entry position so as to regulate movement of the front curtain in a closing direction, and a rear curtain regulation portion which can be locked by the rear curtain locking portion from the other side around the lever axis at the entry position so as to regulate movement of the rear curtain in a closing direction.